Trust me guy, i played about 2000 Games with priest, didnt works with Shadow Madness and it will not work with potion of madness.

You silence the minion himself, this not affects the power of Spell you know, its NOT like a debuff/buff ON the minion +1/+1 and as long as the minion is still in play after your finished your turtn, it will go back to its owners side.

Let me change your mind, only better because you can play it on turn 1. The best targets are deathrattles that dies on your board so the deathrattle triggers. Priest is going to be OP af in wild and tier 2-3 in standard. 2 pint-size potions and this and you can steal tyrion for 3 mana 😛